Poly-3,4-ethylenedioxythiophene (“PEDOT”) prepared from 3,4-ethylenedioxythiophene (“EDOT”) is a well known conducting polymer. Higher photopic contrast and a more colorless bleached state is obtained by incorporation of an additional methylene unit into the EDOT repeat unit with 3,4-propylenedioxythiophene (“PropOT”). PolyPropOT exhibits enhanced electrochromic properties over conducting polymer PEDOT. PPropOT has a Δ% T of 66% at λmax compared to the 54% transmittance change for PEDOT (Sommen, G. L. Mini-Rev. Org. Chem. 2005, 2, 375).
Theoretical studies and calculations indicate that selenophene based polymers should have a lower band gap (Eg) than corresponding polythiophenes. Due to the larger size of selenium, polyselenophenes are also expected to have some advantages over polythiophenes, such as having lower oxidation and reduction potentials, being easier to polarize, and being more suitable for interchain charge transfer (which is facilitated by the intermolecular contacts between Se atoms).
Poly(3,4-ethylenedioxyselenophene) (“PEDOS”) has been synthesized (Patra, A.; Wijsboom, Y. H.; Zade, S. S.; Li, M.; Sheynin, Y.; Leitus, G.; Bendikov, M. J. Am. Chem. Soc. 2008. 130, 6735) and is reported to exhibit a band gap of 1.4 eV. The polymer PEDOS is highly stable in its oxidized state and has well defined spectroelectrochemistry. It also has a lower band gap than PEDOT (1.6-1.7 eV).
Selenium based conductive polymers offer several challenges. Doped polyselenophenes show significantly lower conductivities (10−4 to 10−1 S/cm) than that of doped polythiophenes (up to 103 S/cm). The lack of a well-defined electrochemical response prevents their study and application and there are synthetic challenges for the synthesis of substituted selenophene-based monomeric precursors. It is presumed that the low conductivity and poor electrochemical behavior of polyselenophenes results from their instability during oxidative polymerization.
Accordingly, there remains a need in the art for new, substituted polyselenophenes with high conductivity and well-defined electrochemistry.